Electrical relay



June 7, 1938. B. E. OHAGAN 7 ,0

ELEC'IR ICAL RELAY I Filed June 19, 1935 INVENTOR Bermzr OHagan.

HIS ATTORNEY Patented June 7, 1938 PATENT OFFICE ELECTRICAL RELAY I Bernard E. OHagan, Swissvale, Pa., assig'nor to I The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application June 19,

I 2 Claims.

My invention relates to electrical relays and circuits therefor, and more particularly to relays and circuits which are especially suitable for use in railway signaling.

Iwill describe one form of relay and relay circuit embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a view, partly diagrammatic and partly in isometric projection, illustrating one form of relay embodying my invention; while Fig. 2 is a diagrammatic view showing one track circuit arrangement in which the relay shown in Fig. 1 may be used.

Similar reference characters refer to similar parts in each of the respective views.

Referring first to Fig. l, the relay'comprises a main electromagnet M having two parallel cores la andlb connected together at their upperends by an H-shaped back strap BS and provided at their lower ends with enlarged pole pieces Ia and 2b, respectively.

The cores la and lb carry the usual operating windings la and 4b connected in series to establish cumulative fluxes in the usual manner.

Attached to the rear sides of the pole pieces Ia and ID is a non-magnetizable bracket 1 which carries two pivot screws 8, only one of which is visible in the drawing. Pivotally mounted on the screws 8 for swinging movement toward or away from the pole pieces Ia and Ib is a tractive armature 9 which carries a contact finger 5 adapted to engage a fixed contact block 5a or 5b, closing a contact 5-5a or 5--5b in the usual and wellknown manner.

The reference character 8 designates a second or auxiliary electromagnet comprising a pair of parallel cores I la and l lb also connected together at their upper ends by the back strap BS. Other parts of magnet S corresponding to those of magnet M are identified by like reference characters, but each part is distinguished by the added prefix 1". The magnet S diflers from magnet M in that a front strap FS of magnetic material is arranged between the ends of poles Ila and llb and their respective pole pieces III: and III). This front strap FS' is provided for the sole purpose of enabling sufficient flux to flow in the auxiliary electromagnet S to saturate the back strap BS with the least expenditure of energy. .The front strap FS need not be provided, but if omitted theampere turns necessary to saturate the back strap will be higher on account 01' the air gap between the pole pieces lIw-lIb and armature l9.

Since the magnetic circuit of each of the elec- 1935, Serial No. 27,414

tromagnets S and M includes a common portion of the back strap BS, it will be evident that the saturation of the ,back strap due to energy flowing over the windings of either electromagnet will. adversely affect the efliciency of the other in pro-- portion to the degree of saturation of the back strap. a

Referring now to Fig. 2, the operation of a novel track 'circuit in which the relay of Fig. l is employed will be-explained. In this figure, the reference characters Ila and Ilb designate the rails of a stretch of railway track, which rails are divided by insulated joints II to form a plurality of track sections, only one complete section, designated by the reference character B, and portions of adjoining sections designated by the ref-, erence characters A and C respectively, being shown. The track section B and the adjoining sections are each provided with a track circuit including a track relay, only the track relays BTR and CTR of sections B and C being shown.

w The track circuit for section B includes windings la and 4b of track relay BTR which are connected across the rails Ila and Ilb at one end of the section B, in series with front contact l5l5a of electromagnet S of the relay BTR, and also includes a track battery B23 which is connected across the rails Ila and Ilb at the other end of the section, in series with the usual current limiting resistor BRl.

The track relay BTR. has its windings Ma and llb connected in series in an energizing circuit including a resistor ARI and the battery A23, which battery feeds energy to the rails Ila and Ilb of section A, through the usual track circuit current limiting resistor ARI. The amount of current received by windings a and-b is determined, in part, by the resistance of a shunt -'path around these windings which path includes a ballast conductor AC, the lower track rail, and the track ballast therebetween. Thus it will be seen that under extremely dry ballast conditions when the resistance of the above shunt path is infinite, the amount of current flowing in windings lla and llb is determined by the voltage of battery AII and the value of resistor ARI. In wet weather, however, the ballast leakage path permits current to flow and produces an additional voltage drop over resistor ARI so that the degree of energization of windings Ila and ill) is reduced and is controlled in accordance with the ballast leakage resistance of the track circuit of section A. The conductor AC may, for example, be a wire or a spare rail fastened to the ties and in electrical contact with the track ballast.

With proper adjustment of resistor AR2 and proper design of the relay elements, the ampere turns of windings Ma and Nb alone will be such as to produce suflicient saturation of the center portion 01 the back strap BS during dry ballast conditions to provide the. necessary increase in reluctance for compensation of the electromagnet M. Under wet ballast conditions, on the other hand, the back strap BS will not be-saturated and the reluctance will be lower so as correspondingly to increase the efliciency of electromagnet M. I It will be seen therefore that the windings Ma and Nb, as herein employed, cause the efficiency of the electromagnet M of the relay BTR to vary in inverse proportion to variations in ballast resistance (i. e., to the energization of windings 4a and 4b) and accordingly the release characteristic of armature 9 which controls contact 5 remains substantially constant irrespective of ballast resistance variations. In this manner, increased shunting sensitivity is obtained since armature 9 will release with a relatively poorer train shunt than if the compensating electromagnet S were not provided.

Some compensation for electromagnet M of relay BTR is, of course, obtained under varying ballast conditions, merely by virtue of the ballast path around the resistor BR! which is provided by the ballast conductor BC. That is, under wet ballast conditions, for example, a shunt path around resistor ER! is provided which path includes the resistor BRZ and the ballast leakage path between the conductor BC and the upper rail 2Ia. Consequently, during wet weather conditions when increased track circuit current is necessary to maintain windings 4a and 4b sufficiently energized, the battery B23 will supply an additional increment of current over the foregoing shunt path. However, due to the presence of resistor BRZ the magnitude of which remains fixed once proper adjustment is made to suit the characteristics of relay CTR, the compensation obtained by means of the above shunt path is incomplete, so that additional means such as are provided through the saturation effect of electromagnet srmust be employed in order that full compensation for ballast resistance variations may be obtained.

The purpose served by front contact I 5| 5a of relay BTR is to check continuously the integrity of the circuit which includes windings 4a and lb. If this circuit should become either open or shortcircuited, electromagnet M will release its armature, thus opening contact 5-5a to provide the necessary indication of the fault.

Although I have herein shown and described only one form of electrical relay and circuit therefor embodying my invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. A relay comprising a main flux path including a saturable back strap and a main armature, a main winding for setting up a flux in said main flux path to attract said main armature, an auxiliary flux path forming a shunt around said back strap and including an auxiliary armature, said auxiliary path having a relatively low reluctance compared to the reluctance of said main path,

and an auxiliary winding on said auxiliary path for setting up a flux in said auxiliary path to at times sati ate said back strap to vary the efliciency of said main flux path.

2. A relay comprising a main flux path including a first pair of cores connected at one end by a saturable back strap, a main armature movable toward and away from the cores of said first pair, a main winding on the cores of said first pair for controlling said main armature, an auxiliary flux path including a second pair of cores and said back strap, an auxiliary armature movable toward and away from said second pair of cores, an auxiliary winding on the cores of said second pair for controlling said second armature and for setting up in said back strap a. flux which affects the eificiency of said main path, and a magnetic shunt bridging the cores of said second pair for enabling sufiicient fiux from said auxiliary winding to flow in said auxiliary path to saturate the "back strap with flux with a minimum expenditure of energy.

BERNARD E. OHAGAN. 

